Summary: How Does Attention Select and Track Spatially Extended Objects?
New Effects of Attentional Concentration and Amplification
George A. Alvarez
Harvard University
Brian J. Scholl
Yale University
Real-world situations involve attending to spatially extended objects, often under conditions of motion
and high processing load. The present experiments investigated such processing by requiring observers
to attentionally track a number of long, moving lines. Concurrently, observers responded to sporadic
probes as a measure of the distribution of attention across the lines. The results revealed that attention
is concentrated at the centers of lines during tracking, despite their uniformity, and that this center
advantage grew as the lines became longer: Not only did observers get worse near the endpoints, but they
became better at the lines' centers, as if attention became more concentrated as the objects became more
extended. These results begin to show how attention is flexibly allocated in online visual processing to
extended dynamic objects.
Keywords: object-based attention, multiple-object tracking
For the last two decades, a major project in the study of visual
attention has been the attempt to characterize the underlying units
of attention--contrasting spatial areas, individual visual features,
and discrete objects. As part of this project, a large literature on